Abstract
We demonstrate a quantum dash quantum cascade photodetector (QDash-QCD) by incorporating self-assembled InAs quantum dashes into the active region of a long wave infrared QCD. Sensitive photoresponse to normal incident light at 10 μm was observed, which is attributed to the intersubband (ISB) transitions in the quantum well/quantum dash (QW/QDash) hybrid absorption region and the following transfer of excited electrons on the extraction stair-like quantum levels separated by LO-phonon energy. The high density InAs quantum dashes were formed in the Stranski-Krastanow mode and stair-like levels were formed by a lattice matched InGaAs/InAlAs superlattice. A stable responsivity from 5 mA/W at 77 K to 3 mA/W at as high as 190 K was observed, which makes the QDash-QCD promising in high temperature operation.
Highlights
Quantum cascade photodetector is one kind of ISB photodetectors based on electrons’ transitions between quantized subbands in the conduction band of semiconductor heterostructures
The computation was based on a simplified model by solving one-dimensional Schrödinger equation under envelopefunction approximation without considering the quantum confinement of QDashes in the growth plane
The dominant transition is between the hybrid levels A1 and A2, similar to the Quantum well (QW)/quantum dot (QD) mixed mode reported in ref. [18, 19, 23, 24], leading to a detection wavelength of 10 μm
Summary
Quantum cascade photodetector is one kind of ISB photodetectors based on electrons’ transitions between quantized subbands in the conduction band of semiconductor heterostructures. Quantum cascade photodetector (QCD) works without an external bias voltage due to asymmetric conduction band profile. This asymmetry is derived from the stairlike subbands separated by LO-phonon energy by choosing appropriate layer thicknesses of the superlattice in the extraction region. This design guarantees a negligible dark current, which makes QCDs promising in large focal plan array and small pixel applications [1, 2]. The absorption of normal incident light was limited by polarization selection rule for ISB transitions in quantum wells, which restricts the possible
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